Cellulose nanocrystals (CNCs) are obtained by the acid hydrolysis of native cellulose using an aqueous inorganic acid, such as sulphuric acid. Upon the completion (or near completion) of acid hydrolysis of the amorphous regions of native cellulose, individual rod-like cellulose crystallites of nanometer dimensions (commonly referred to as cellulose nanocrystals (CNCs)) that are insensitive to acidic environment are obtained. CNC possesses excellent mechanical properties, biodegradability and biocompatibility with a diameter ranging between 5 and 20 nm and length ranging to a few hundred nanometers.
The hydrolysis of cellulose using sulphuric acid leads to the formation of sulfate ester groups generating numerous negative charges on the surface of CNCs. These negative charges on the surface of CNCs promote uniform dispersion of nanocrystals due to electrostatic repulsion in aqueous solutions. The functionalization or coating of CNC with polymers or oligomers has been pursued however, many methods involve reaction systems that are difficult to scale industrially.
Carbon fiber that is lightweight and good in mechanical strength has become an attractive material for a wide variety of advanced applications. Most of the carbon fibers are currently produced through the carbonization of the petroleum-based polyacrylonitrile (PAN) as the dominant precursor but PAN has the drawback of being costly and high in alkaline metal content.